AC Propulsion Introduces Real-World Emission Measurement

 AC Propulsion Introduces
Real-World Emission Measurement

November 13, 1997
Rosamond, CA

AC Propulsion Inc., known for its advanced electric vehicle power system products, unveiled a product for combustion-engine vehicles today at the Willow Springs International Raceway. The new product allows in-car, on-road, real-time measurement of tailpipe emissions. "We call it real-world measurement because it takes emission measurement out of the laboratory and onto the road where emissions can be measured according to the way people really drive" said Tom Gage, AC Propulsion Business Manager.

AC Propulsion engineers miniaturized a system that works according to the same basic principals used in the multi-million dollar emission testing laboratories employed by auto companies, the US EPA, and the California Air Resources Board. The AC Propulsion in-car system measures exhaust gas flow, emission concentration, and distance traveled and then accurately calculates emission flow rates in grams per mile. It operates from the vehicle's 12 V battery and fits in one of the passenger seats.

AC Propulsion began to design the on-road emission measurement system while developing emission controls for its Long Ranger* trailer, a gasoline-fueled generator used to extend the range of electric vehicles. "It's hard to realistically measure emissions of a hybrid power system over a standard dynamometer driving test so we thought it would be great to just plug in an instrument, go for a drive, and get real emission data" said Gage. "Then we realized that we could also test these new cars (LEVs and ULEVs) that the auto companies say are almost as clean as EVs, and see how clean they really are. That's when we really got motivated".

Early tests with a system prototype have yielded interesting results suggesting that new cars can pollute much more in real world driving than laboratory tests indicate. For example, real-world measurement of a 1998 model vehicle certified to California's Low Emission Vehicle (LEV) standards showed carbon monoxide (CO) emissions at almost four times the certification level. During the same test, nitric oxides (NOx) emissions were almost twice the certification limit. This result came from a 10 mile highway course that included a full power freeway merge and two uphill accelerations from 55 to 75 mph. "Typical LA driving", noted Gage.

In comparison, emissions from series-hybrid vehicles in which the engine operates at a constant output, do not vary by much no matter how the vehicle is driven. The emission profile is de-coupled from the driving mode. Once the hybrid engine is clean, the emissions are predictable for any driving cycle. "We measured emissions from the Long Ranger* and the grams per mile only changed slightly no matter how hard we drove. And the Long Ranger* does run clean", said Gage, "we are almost at the ULEV standard the way it runs right now."

AC Propulsion sees a real market for the in-car system because its small size, low potential cost, and good accuracy make it an ideal tool for the development and testing of automotive emissions. By allowing a much broader range of vehicle operating conditions to be studied directly, in-car emission measurement will enable automotive engineers to design emission controls that perform better in real world driving. "Given the auto companies' huge commitment to building cleaner cars, I think we can sell these instruments by the thousands", Gage observed. "If we can get the price low enough, we might even be able to sell a few to car magazines for their road test kits".